Adhesive composition, bio-electrode, method for manufacturing a bio-electrode, and salt

ABSTRACT

An adhesive composition including a resin and electro-conductive material, wherein the electro-conductive material is an ammonium salt of fluorosulfonic acid having 5 or more carbon atoms shown by the general formula (1): (R 1 —X—Z—SO 3   − ) n  M n+  (1), wherein, R 1  represents a monovalent hydrocarbon group having 1 to 40 carbon atoms and optionally substituted by a heteroatom or optionally interposed by heteroatom; X represents any of a single bond, ether group, ester group, and amide group; Z represents an alkylene group having 2 to 4 carbon atoms, containing 1 to 6 fluorine atoms, and optionally containing a carbonyl group; M +  represents a cation having one or two ammonium cation structures. This can form a living body contact layer for a bio-electrode with excellent electric conductivity, biocompatibility, and light weight, which manufactures at low cost and does not cause large lowering of the electric conductivity even when it is wetted with water or dried.

TECHNICAL FIELD

The present invention relates to a bio-electrode, which is in contactwith living skin and can detect physical conditions such as a heart rateon the basis of electric signals from the skin, and a method formanufacturing the same, as well as an adhesive composition and salt thatcan be suitably used for a bio-electrode.

BACKGROUND ART

In recent years, wearable devices have been developed progressively withthe spread of Internet of Things (IoT). Representative examples thereofinclude a watch and glasses that can be connected with internet.Wearable devices that can always monitor physical conditions are alsonecessary in a medical field and a sports field, and are expected to bea growth field in the future.

In the medical field, wearable devices have been investigated to monitororganic conditions by sensing a weak current such as anelectrocardiogram measurement, which detects heart beats by electricsignals. The electrocardiogram is measured by fitting a body withelectrodes on which electro-conductive paste is applied, and thismeasurement is performed only once in a short period of time. On theother hand, the aim of development of the foregoing medical wearabledevice is to develop devices that monitor health conditions continuouslyfor several weeks. Accordingly, bio-electrodes used for a medicalwearable device have to keep the electric conductivity unchanged and notto cause skin allergies even when being used for a long time. Inaddition to these, it is desirable that the bio-electrode is light inweight and can be manufactured at low cost.

Medical wearable devices include a type in which the device is attachedto a body and a type in which the device is incorporated into clothes.As the type in which the device is attached to a body, it has beenproposed a bio-electrode using water soluble gel containing water andelectrolyte, which are materials of the foregoing electro-conductivepaste (Patent Document 1). On the other hand, as the type in which thedevice is incorporated into clothes, it has been proposed a means to usecloth in which an electro-conductive polymer such aspoly-3,4-ethylenedioxythiophene-polystyrenesulfonate (PEDOT-PSS) orsilver paste is incorporated into the fibers for electrodes (PatentDocument 2).

When using the foregoing water soluble gel containing water andelectrolyte, however, the electric conductivity is lost as the water islost due to drying. On the other hand, some people can cause skinallergies by the use of metal with high ionization tendency such ascopper. The use of an electro-conductive polymer such as PEDOT-PSS alsohas a risk of skin allergies due to the strong acidity of theelectro-conductive polymer.

As the electrode material, it has been investigated to use metalnanowire, carbon black, and carbon nanotube since they have excellentelectric conductivity (Patent Documents 3, 4, and 5). The metal nanowirecan conduct electricity in a small loading amount since the wires arebrought into contact with each other in high probability. The metalnanowire, however, can cause skin allergies since they are thin materialwith sharp tips. The carbon nanotube also has stimuli to a living bodyby the same reason. The carbon black has some irritativeness to skin,although the toxicity is lower than the carbon nanotube. As describedabove, the biocompatibility is sometimes worsened due to the shape andirritativeness of a material, even though the material itself does notcause an allergic reaction. Accordingly, it has been difficult toachieve both the electric conductivity and the biocompatibility.

As a means for solving these problems, it has been investigated to useelectro-conductive metal particles as an electrode material. Amongmetals, noble metals such as gold, platinum, and silver, which havelowest ionization tendencies, are hard to cause skin allergies.Accordingly, it is possible to achieve both the electric conductivityand the biocompatibility by using these noble metal particles. Whenmixing these noble metal particles into a resin, however, electricity isnot conducted unless the particles are brought into contact with eachother in the resin, which is an insulator. In order to bring theparticles into contact with each other, the noble metal particles haveto be loaded in a volume ratio of 70% or more. As described above, whenusing metal particles, it is necessary to load a large amount ofexpensive noble metal particles, and accordingly, the production costbecomes very high and the weight increases, thereby making it impossibleto achieve weight reduction, which is necessary for wearable devices.

When the bio-electrode is away from skin, it becomes impossible toobtain information from the body. Just the change of contact areafluctuates the quantity of electricity to be conducted, therebyfluctuating the baseline of an electrocardiogram (electric signals).Accordingly, the bio-electrode have to be in contact with skincontinually without changing the contact area in order to obtain stableelectric signals from a body. For that purpose, the bio-electrodepreferably has tackiness. It also needs elasticity and flexibility tocope with expansion and contraction as well as change of bending ofskin.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: International Patent Laid-Open Publication No. WO2013/039151

Patent Document 2: Japanese Unexamined Patent Application Publication(Kokai) No. 2015-100673

Patent Document 3: Japanese Unexamined Patent Application Publication(Kokai) No. H5-095924

Patent Document 4: Japanese Unexamined Patent Application Publication(Kokai) No. 2003-225217

Patent Document 5: Japanese Unexamined Patent Application Publication(Kokai) No. 2015-019806

SUMMARY OF INVENTION Technical Problem

The present invention has been accomplished to solve the foregoingproblems, and an object thereof is to provide an adhesive compositionthat can form a living body contact layer for a bio-electrode withexcellent electric conductivity and biocompatibility as well as lightweight, which can be manufactured at low cost and does not cause largelowering of the electric conductivity even when it is wetted with wateror dried; a bio-electrode in which the living body contact layer isformed from the adhesive composition; and a method for manufacturing thesame.

Solution to Problem

To achieve the object, the present invention provides an adhesivecomposition comprising a resin and an electro-conductive material,wherein the electro-conductive material is an ammonium salt offluorosulfonic acid having 5 or more carbon atoms shown by the followinggeneral formula (1),

(R¹—X—Z—SO₃ ⁻)_(n)M^(n+)  (1)

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; X representsany of a single bond, an ether group, an ester group, and an amidegroup; Z represents a linear or branched alkylene group having 2 to 4carbon atoms, containing 1 to 6 fluorine atoms, and optionallycontaining a carbonyl group; M^(n+) represents a cation having one ortwo ammonium cation structures; and “n” is 1 when the number of theammonium cation structure contained in the M^(n+) is one, or is 2 whenthe number of the ammonium cation structure contained in the M^(n+) istwo.

Such an adhesive composition can be an adhesive composition that canform a living body contact layer for a bio-electrode with excellentelectric conductivity and biocompatibility as well as light weight,which can be manufactured at low cost and does not cause large loweringof the electric conductivity even when it is wetted with water or dried.

It is preferable that the electro-conductive material be shown by thefollowing general formula (1-1) or (1-2),

wherein, R¹ and X have the same meanings as defined above; Rf₁ to Rf₄each independently represent an atom or a group selected from a hydrogenatom, a fluorine atom, a methyl group, an ethyl group, and atrifluoromethyl group, with the proviso that one or more of Rf₁ to Rf₄is a fluorine atom or a trifluoromethyl group, and Rf₁ and Rf₂ areoptionally combined with each other to form a carbonyl group; R² to R¹¹each independently represent a hydrogen atom, a linear, branched, orcyclic alkyl group having 1 to 20 carbon atoms, a linear, branched, orcyclic alkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom, and R² and R³ optionally form a ringwith each other together with the nitrogen atom bonded to R² and R³; andY represents a linear or branched alkylene group having 2 to 16 carbonatoms optionally having one or more groups selected from an ester groupand a thioester group.

The bio-electrode, containing such an electro-conductive material, ismore superior in electric conductivity and biocompatibility, and causesless lowering of the electric conductivity when it is wetted with wateror dried.

It is preferable that the electro-conductive material have apolymerizable double bond or a hydroxy group in either or both of theanion and the cation.

The bio-electrode, containing such an electro-conductive material,causes less lowering of the electric conductivity when it is wetted withwater or dried because the electro-conductive material reacts with theresin and binds thereto when the adhesive composition is cured.

It is preferable that the resin be one or more resins selected fromsilicone resin, acrylic resin, and urethane resin.

The adhesive composition that contains such resin can form a living bodycontact layer that is excellent in compatibility with theelectro-conductive material, adhesion properties to theelectro-conductive material, tackiness to skin, elasticity, andrepellency, in particular.

It is preferable that the adhesive composition further comprise a carbonmaterial.

Such an adhesive composition containing a carbon material can form aliving body contact layer that has more favorable electric conductivity.

It is preferable that the carbon material be either or both of carbonblack and carbon nanotube.

Such a carbon material can be particularly preferably used in theinventive adhesive composition.

The present invention also provides a bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material, wherein the living body contactlayer is a cured material of the foregoing adhesive composition.

Such a bio-electrode can be a bio-electrode having a living body contactlayer with excellent electric conductivity and biocompatibility as wellas light weight, which can be manufactured at low cost and does notcause large lowering of the electric conductivity even when it is wettedwith water or dried.

It is preferable that the electro-conductive base material comprises oneor more species selected from gold, silver, silver chloride, platinum,aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless,chromium, titanium, and carbon.

Such an electro-conductive base material can be particularly preferablyused in the inventive bio-electrode.

The present invention also provides a method for manufacturing abio-electrode having an electro-conductive base material and a livingbody contact layer formed on the electro-conductive base material,comprising: applying the foregoing adhesive composition onto theelectro-conductive base material; and curing the adhesive composition;thereby forming the living body contact layer.

Such a production method makes it possible to manufacture abio-electrode having a living body contact layer easily and at low cost,which is excellent in electric conductivity and biocompatibility as wellas light in weight without causing large lowering of the electricconductivity even when it is wetted with water or dried.

It is preferable that the electro-conductive base material comprise oneor more species selected from gold, silver, silver chloride, platinum,aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless,chromium, titanium, and carbon.

Such an electro-conductive base material can be particularly preferablyused in the inventive method for manufacturing a bio-electrode.

The present invention also provides a salt shown by the followinggeneral formula (2):

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; R⁶ to R¹¹ eachindependently represent a hydrogen atom, a linear, branched, or cyclicalkyl group having 1 to 20 carbon atoms, a linear, branched, or cyclicalkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom; and Y represents a linear or branchedalkylene group having 2 to 16 carbon atoms optionally having one or moregroups selected from an ester group and a thioester group.

Such a salt, having excellent electric conductivity and very lowsolubility in water, is suitable for an electro-conductive material usedfor the inventive adhesive composition in particular.

Advantageous Effects of Invention

As described above, the inventive adhesive composition can form a livingbody contact layer for a bio-electrode that can efficiently conductelectric signals from skin to a device (i.e., having excellent electricconductivity), is free from the risk of causing allergies even when itis worn on skin for a long time (i.e., having excellentbiocompatibility), is light in weight, can be manufactured at low cost,and does not cause large lowering of the electric conductivity even whenit is wetted with water or dried. The electric conductivity can be moreimproved by adding a carbon material, and a bio-electrode withparticularly high adhesion and high elasticity can be manufactured bycombining resin with tackiness and elasticity. The elasticity andtackiness to skin can be improved by additives, and can be adjusted byadjusting the composition of the resin and the thickness of the livingbody contact layer appropriately. Accordingly, the inventivebio-electrode, with the living body contact layer being formed by usingsuch an inventive adhesive composition, is particularly suitable as abio-electrode used for a medical wearable device. Moreover, theinventive method for manufacturing a bio-electrode can manufacture sucha bio-electrode easily at low cost. Furthermore, the inventive salt,having excellent electric conductivity and very low solubility in water,is suitable for an electro-conductive material used for the inventiveadhesive composition in particular.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view showing an example of the inventivebio-electrode;

FIG. 2 is a schematic sectional view showing an example of the inventivebio-electrode worn on a living body;

FIG. 3(a) is a schematic view of the bio-electrode produced in Examplesof the present invention viewed from the living body contact layer side;and FIG. 3(b) is a schematic view of the bio-electrode produced inExamples of the present invention viewed from the electro-conductivebase material side; and

FIG. 4 is a photograph of a scene of measuring impedance on the surfaceof skin by using the bio-electrode produced in Examples of the presentinvention.

DESCRIPTION OF EMBODIMENTS

As described above, it has been desired to develop an adhesivecomposition that can form a living body contact layer for abio-electrode with excellent electric conductivity and biocompatibilityas well as light weight, which can be manufactured at low cost and doesnot cause large lowering of the electric conductivity even when it iswetted with water or dried; a bio-electrode in which the living bodycontact layer is formed from the adhesive composition; and a method formanufacturing the same.

The present inventors noticed ionic liquids as an electro-conductivematerial to be blended to an adhesive composition for forming a livingbody contact layer for a bio-electrode. Ionic liquids are characterizedby high thermal and chemical stability as well as excellent electricconductivity, thereby having been widely used for battery uses.Illustrative examples of known ionic liquid include hydrochloric acidsalt, hydrobromic acid salt, hydroiodic acid salt,trifluoromethanesulfonic acid salt, nonafluorobutanesulfonic acid salt,bis(trifluoromethanesulfonyl)imidic acid salt, hexafluorophosphate salt,and tetrafluoroborate salt of sulfonium, phosphonium, ammonium,morpholinium, pyridinium, pyrrolidinium, and imidazolium. However, thesesalts (particularly, the ones with low molecular weight) are generallyliable to hydrate, thereby causing a bio-electrode to lower the electricconductivity due to extraction of the salt with perspiration or bywashing when these salts are added to an adhesive composition to formthe living body contact layer. The tetrafluoroborate salt is highlytoxic, and the other salts have high solubility in water to easilypermeate into skin, each of which causes rough dry skin (i.e., highlyirritative to skin).

The present inventors have diligently investigated to solve theforegoing subject and have consequently found that an ammonium salt offluorosulfonic acid having 5 or more carbon atoms and containing 1 to 6fluorine atoms at the particular part, which has very low solubility inwater, can considerably decrease the risk of causing rough dry skin andlowering the electric conductivity due to extraction with perspiration.The present inventors also have found that this salt, being mixed intoan adhesive mass (resin such as silicone type, acrylic type, andurethane type) to form a living body contact layer, enable abio-electrode to cope with both electric conductivity andbiocompatibility without causing large lowering of the electricconductivity even when it is wetted with water or dried, and to functionas a bio-electrode that can be in contact with skin continually toobtain stable electric signals from a body in a long period; therebycompleting the present invention.

That is, the present invention is an adhesive composition comprising aresin and an electro-conductive material, wherein the electro-conductivematerial is an ammonium salt of fluorosulfonic acid having 5 or morecarbon atoms shown by the following general formula (1),

(R¹—X—Z—SO₃ ⁻)_(n)M^(n+)  (1)

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; X representsany of a single bond, an ether group, an ester group, and an amidegroup; Z represents a linear or branched alkylene group having 2 to 4carbon atoms, containing 1 to 6 fluorine atoms, and optionallycontaining a carbonyl group; M^(n+) represents a cation having one ortwo ammonium cation structures; and “n” is 1 when the number of theammonium cation structure contained in the M^(n+) is one, or is 2 whenthe number of the ammonium cation structure contained in the M^(n+) istwo.

Hereinafter, the present invention will be specifically described, butthe present invention is not limited thereto.

<Adhesive Composition>

The inventive adhesive composition contains an electro-conductivematerial and resin. Hereinafter, each component will be describedfurther specifically.

[Electro-Conductive Material (Salt)]

The salt to be blended as an electro-conductive material to theinventive adhesive composition is an ammonium salt of fluorosulfonicacid having 5 or more carbon atoms shown by the following generalformula (1),

(R¹—X—Z—SO₃ ⁻)_(n)M^(n+)  (1)

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; X representsany of a single bond, an ether group, an ester group, and an amidegroup; Z represents a linear or branched alkylene group having 2 to 4carbon atoms, containing 1 to 6 fluorine atoms, and optionallycontaining a carbonyl group; M^(n+) represents a cation having one ortwo ammonium cation structures; and “n” is 1 when the number of theammonium cation structure contained in the M^(n+) is one, or is 2 whenthe number of the ammonium cation structure contained in the M^(n+) istwo.

The salt to be blended as an electro-conductive material to theinventive adhesive composition is preferably a salt shown by thefollowing general formula (1-1) or (1-2),

wherein, R¹ and X have the same meanings as defined above; Rf₁ to Rf₄each independently represent an atom or a group selected from a hydrogenatom, a fluorine atom, a methyl group, an ethyl group, and atrifluoromethyl group, with the proviso that one or more of Rf₁ to Rf₄is a fluorine atom or a trifluoromethyl group, and Rf₁ and Rf₂ areoptionally combined with each other to form a carbonyl group; R² to R¹¹each independently represent a hydrogen atom, a linear, branched, orcyclic alkyl group having 1 to 20 carbon atoms, a linear, branched, orcyclic alkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom, and R² and R³ optionally form a ringwith each other together with the nitrogen atom bonded to R² and R³; andY represents a linear or branched alkylene group having 2 to 16 carbonatoms optionally having one or more groups selected from an ester groupand a thioester group.

R¹ represents a linear, branched, or cyclic monovalent hydrocarbon grouphaving 1 to 40 carbon atoms and optionally substituted by a heteroatomor optionally interposed by a heteroatom. Illustrative examples of R¹include an alkyl group, an alkenyl group, an alkynyl group having 1 to40, preferably 3 to 30 carbon groups, an aryl group, an aralkyl group,and a heteroaromatic group having 4 to 16, preferably 6 to 12 carbonatoms; which may have a halogen atom, a silicon atom, a sulfur atom, anitrogen atom, a hydroxy group, a carboxy group, a carbonyl group, anether group, a thiol group, an ester group, a carbonate group, an amidegroup, an urethane group, an amino group, an alkoxycarbonyl-substitutedamino group, a sultone group, a lactam group, a sulfoneamide group, anazide group, a sulfonyl group, a sulfonyloxy group, a cyano group,and/or a nitro group.

Illustrative examples of the fluorosulfonate anion of the salt shown bythe foregoing general formula (1-1) or (1-2) include the following.

The cation of the salt shown by the foregoing general formula (1-1) or(1-2) is a cation that has one or two ammonium cation structures. Theammonium cation structures include NH₄ ⁺ as well as primary, secondary,tertiary, and quaternary ammonium cation structures; among them,tertiary and quaternary ammonium cation structures are preferable.Illustrative examples of the cation having one or two tertiary orquaternary ammonium cation structures include the following.

Among the foregoing anions and cations, the ones having a polymerizabledouble bond or a hydroxy group are particularly preferable because theyeach react with the resin (base resin) and binds thereto when theadhesive composition is cured to remain in the living body contact layereven when it is wetted with water, not being extracted from the livingbody contact layer.

The salt shown by the foregoing general formula (1-1) or (1-2) can besynthesized by a method described in Japanese Unexamined PatentApplication Publication (Kokai) No. 2010-113209. Specifically, it can beobtained by a method in which sodium fluorosulfonate containing theforegoing fluorosulfonate anion is mixed with ammonium chloridecontaining one or two ammonium cation structures described above inorganic solvent, for example. In this case, sodium chloride formed as abi-product is preferably removed by washing with water.

The amount of the salt to be blended as an electro-conductive materialis preferably in a range of 0.1 to 200 parts by mass, more preferably ina range of 1 to 100 parts by mass on the basis of 100 parts by mass ofthe resin. The salt may be blended alone or in combination of two ormore kinds.

It is to be noted that Japanese Unexamined Patent ApplicationPublication (Kokai) No. 2008-039815 and Japanese Unexamined PatentApplication Publication (Kokai) No. 2010-113209 describe part of thesalts blended as an electro-conductive material in the inventiveadhesive composition. However, these Patent Application Publication onlydescribe the salt as a thermal-acid generator blended to a resistunderlayer film material.

[Resin]

The resin to be blended to the inventive adhesive composition is acomponent to prevent elution of the foregoing electro-conductivematerial (salt) from a living body contact layer to retain the salt. Theresin is preferably either or both of heat-curable (thermosetting) resinor photo-curable resin, particularly one or more resins selected fromsilicone resin, acrylic resin, and urethane resin.

The silicone resin include an addition-curable (additionreaction-curable) type and a radical curable (radical crosslinkingreaction-curable) type. As the addition-curable type, it is possible touse one that contains diorganosiloxane having an alkenyl group(s), MQresin having an R²⁰ ₃SiO_(0.5) unit and an SiO₂ unit,organohydrogenpolysiloxane having plurality of SiH groups, platinumcatalyst, an addition reaction inhibitor, and organic solvent, forexample, described in Japanese Unexamined Patent Application Publication(Kokai) No. 2015-193803. As the radical curable type, it is possible touse one that contains diorganopolysiloxane with or without an alkenylgroup, MQ resin having an R²⁰ ₃SiO_(0.5) unit and an SiO₂ unit, organicperoxide, and organic solvent, for example, described in JapaneseUnexamined Patent Application Publication (Kokai) No. 2015-193803.Herein, R²⁰ represents substituted or unsubstituted monovalenthydrocarbon group having 1 to 10 carbon atoms.

It is also possible to use a polysiloxane-resin integrated compound thatis formed by condensation reaction of MQ resin and polysiloxane havingsilanol at the terminal or the side chain of the polymer. The MQ resinimproves the tackiness by the addition thereof because it contains manysilanol, but does not bind to polysiloxane in molecular level because itis not crosslinkable. The tackiness can be increased by integrating thepolysiloxane and the MQ resin as described above.

The silicone resin may contain modified siloxane that has a groupselected from an amino group, an oxirane group, an oxetane group, apolyether group, a hydroxy group, a carboxy group, a mercapto group, amethacryl group, an acryl group, a phenol group, a silanol group, acarboxylic anhydride group, an aryl group, an aralkyl group, an amidegroup, an ester group, and a lactone ring. The addition of modifiedsiloxane improves dispersibility of the electro-conductive material(salt) in the silicone resin. The modified siloxane may be modified atany of the single terminal, the both terminal, or the side chain of thesiloxane.

As the acrylic resin, it is possible to use one having hydrophilic(meth)acrylic ester and hydrophobic long chain (meth)acrylic ester asthe repeating units described in Japanese Unexamined Patent ApplicationPublication (Kokai) No. 2016-011338, for example. In some cases, it isalso possible to copolymerize (meth)acrylic ester having a functionalgroup or (meth)acrylic ester having a siloxane bond.

As the urethane resin, it is possible to use one having an urethane bondwith a polyether bond, polyester bond, polycarbonate bond, or siloxanebond described in Japanese Unexamined Patent Application Publication(Kokai) No. 2016-065238, for example.

In the inventive adhesive composition, the resin preferably has highcompatibility with the foregoing salt to prevent lowering of theelectric conductivity due to elution of salt from the living bodycontact layer. In the inventive adhesive composition, the resinpreferably has high adhesive properties to the electro-conductive basematerial to prevent delamination of the living body contact layer fromthe electro-conductive base material. In order to increase thecompatibility of resin with the salt and the adhesive properties ofresin to the electro-conductive base material, the use of resin withhigh polarity is effective. Illustrative examples of such resin includeresin having one or more moieties selected from an ether bond, an esterbond, an amide bond, an imide bond, an urethane bond, a thiourethanebond, and a thiol group; as well as polyacrylic resin, polyamide resin,polyimide resin, polyurethane resin, and polythiourethane resin. On theother hand, the living body contact layer is in contact with a livingbody, thereby being susceptible to perspiration. Accordingly, in theinventive adhesive composition, the resin preferably has highrepellency, and is hardly hydrolyzed. To make the resin be highlyrepellent and hardly hydrolyzed, the use of silicon-containing resin iseffective.

The silicon atom-containing polyacrylic resin includes a polymer thathas a silicone main chain and a polymer that has a silicon atom(s) onthe side chain, each of which can be suitably used. As the polymer thathas a silicone main chain, silsesquioxane or siloxane having a(meth)acrylpropyl group and so on can be used. In this case, an additionof a photoradical generator allows the (meth)acryl moiety to polymerizeto cure.

As the silicon atom-containing polyamide resin, it is possible tosuitably use polyamide silicone resins described in Japanese UnexaminedPatent Application Publication (Kokai) No. 2011-079946 and U.S. Pat. No.5,981,680, for example. Such a polyamide silicone resin can besynthesized by combining a silicone or non-silicone compound havingamino groups at the both terminals and a non-silicone or siliconecompound having carboxy groups at the both terminals.

It is also possible to use polyamic acid before cyclization thereof,which is obtained by reacting carboxylic anhydride and amine. Thecarboxy group of the polyamic acid may be crosslinked by using acrosslinking agent such as an epoxy type and an oxetane type. It is alsopossible to esterify the carboxy group with hydroxyethyl (meth)acrylateto perform photoradical crosslinking of the (meth)acrylate moiety.

As the silicon atom-containing polyimide resin, it is possible tosuitably use polyimide silicone resins described in Japanese UnexaminedPatent Application Publication (Kokai) No. 2002-332305, for example.Although polyimide resins have very high viscosity, it can be changed tohave low viscosity by blending a (meth)acrylic monomer as a solvent anda crosslinking agent.

Illustrative examples of the silicon atom-containing polyurethane resininclude polyurethane silicone resins. These polyurethane silicone resinscan be crosslinked through urethane bond by blending a compound havingisocyanate groups at the both terminals and a compound having a hydroxygroup(s) at the terminal(s), followed by heating thereof. In this case,a silicon atom(s) (siloxane bond) have to be contained in either or bothof the compound having isocyanate groups at the both terminals and thecompound having a hydroxy group(s) at the terminal(s). Alternatively, anurethane (meth)acrylate monomer and polysiloxane can be blended andcrosslinked by radicals, which are generated by light or heat, asdescribed in Japanese Unexamined Patent Application Publication (Kokai)No. 2005-320418. It is also possible to photo-crosslink a polymer havingboth of a siloxane bond(s) and an urethane bond(s), with the terminalhaving a (meth)acrylate group(s).

The silicon atom-containing polythiourethane resin can be obtained byreacting a compound having a thiol group(s) and a compound having anisocyanate group(s), provided that either of them have to contain asilicon atom(s). It can also be photo-cured if (meth)acrylate groups arecontained at the terminals.

The silicone resin improves the compatibility with the foregoing salt byadding modified siloxane that has a group selected from an amino group,an oxirane group, an oxetane group, a polyether group, a hydroxy group,a carboxy group, a mercapto group, a methacryl group, an acryl group, aphenol group, a silanol group, a carboxylic anhydride group, an arylgroup, an aralkyl group, an amide group, an ester group, and a lactonering in addition to the diorganosiloxane having an alkenyl group(s), MQresin having an R²⁰ ₂SiO_(0.5) unit and an SiO₂ unit, andorganohydrogenpolysiloxane having plurality of SiH groups.

As will be described later, the living body contact layer is a curedmaterial of the adhesive composition. Curing thereof improves theadhesion properties of the living body contact layer to both of skin andthe electro-conductive base material. The curing means is not limited,and common means can be used, including crosslinking reaction by eitheror both of heat and light, an acid catalyst, or a base catalyst. Thecrosslinking reaction can be performed by appropriately selecting acrosslinking method described in “Kakyou han-nou handbook (handbook ofcrosslinking reaction)”, Yasuharu Nakamura, Maruzen shuppan (2013).

The diorganosiloxane having an alkenyl group(s) andorganohydrogenpolysiloxane having plurality of SiH groups can becrosslinked through an addition reaction with a platinum catalyst.

Illustrative examples of the platinum catalyst include platinum-basedcatalysts such as platinic chloride, alcohol solution of platinicchloride, reaction product of platinic chloride and alcohol, reactionproduct of platinic chloride and an olefin compound, reaction product ofplatinic chloride and vinyl group-containing siloxane, a platinum-olefincomplex, a complex of platinum and vinyl group-containing siloxane;platinum group metal-based catalysts such as a rhodium complex and aruthenium complex. These catalysts may be used after dissolved ordispersed in alcohol solvent, hydrocarbon solvent, or siloxane solvent.

The amount of platinum catalyst is preferably in a range of 5 to 2,000ppm, particularly in a range of 10 to 500 ppm on the basis of 100 partsby mass of the resin.

When the addition curable silicone resin is used, an addition reactioninhibitor may be added. This addition reaction inhibitor is added as aquencher to prevent the platinum catalyst from acting in the solvent orunder a low temperature circumstance after forming the coating film andbefore heat curing. Illustrative examples thereof include3-methyl-1-butyn-3-ol, 3-methyl-1-penthyn-3-ol,3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol,3-methyl-3-trimethylsiloxy-1-butyne,3-methyl-3-trimethylsiloxy-1-penthyne,3,5-dimethyl-3-trimethylsiloxy-1-hexyne,1-ethynyl-1-trimethylsiloxycyclohexane,bis(2,2-dimethyl-3-butynoxy)dimethylsilane,1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and1,1,3,3-tetramethyl-1,3-divinyldisiloxane.

The amount of addition reaction inhibitor is preferably in a range of 0to 10 parts by mass, particularly in a range of 0.05 to 3 parts by masson the basis of 100 parts by mass of the resin.

Illustrative examples of photo-curing method include a method of addinga photoradical generator to generate radical by light, together withusing resin having a (meth)acrylate terminal(s) or an olefin terminal(s)or adding a crosslinking agent with the terminal(s) being(meth)acrylate, olefin, or a thiol group(s); and a method of adding aphoto-acid generator to generate acid by light, together with usingresin or a crosslinking agent having an oxirane group(s), an oxetanegroup(s), or a vinyl ether group(s).

Illustrative examples of the photoradical generator includeacetophenone, 4,4′-dimethoxybenzyl, benzyl, benzoin, benzophenone,2-benzoylbenzoic acid, 4,4′-bis(dimethylamino)benzophenone,4,4′-bis(diethylamino)benzophenone, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutylether, 4-benzoylbenzoic acid,2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, methyl2-benzoylbenzoic acid,2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone,4,4′-dichlorobenzophenone, 2,2-diethoxyacetophenone,2,2-dimethoxy-2-phenylacetophenone, 2, 4-diethylthioxanthen-9-one,diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1,4-dibenzoylbenzene,2-ethylanthraquinone, 1-hydroxycyclohexyl phenyl ketone,2-hydroxy-2-methylpropiophenone,2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone,2-isonitrosopropiophenone, and2-phenyl-2-(p-toluenesulfonyloxy)acetophenone (BAPO).

The curing can also be performed by adding a radical generator of a heatdecomposition type. Illustrative examples of the thermal radicalgenerator include 2,2′-azobis(isobutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylbutyronitrile), 4,4′-azobis(4-cyanovaleric acid),2,2′-azobis(methylpropionamidine) hydrochloride,2,2′-azobis[2-(2-imidazolin-2-yl)propane] hydrochloride,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(cyclohexane-1-carbonitrile),1[(1-cyano-1-methylethyl)azo]formamide,2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis[N-(2-propenyl)-2-methylpropionamide],2,2′-azobis(N-butyl-2-methylpropionamide),dimethyl-2,2′-azobis(isobutylate), 4,4′-azobis(4-cyanopentanoic acid),dimethyl-2,2′-azobis(2-methylpropionate), benzoyl peroxide, tert-butylhydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide,di-tert-amyl peroxide, di-n-butyl peroxide,dimethyl-2,2′-azobis(2-methylpropionate), and dicumyl peroxide.

Illustrative examples of the photo-acid generator include sulfoniumsalt, iodonium salt, sulfonyldiazomethane, N-sulfonyloxyimide, andoxime-O-sulfonate type acid generators. Specific examples of thephoto-acid generator is described in paragraphs [0122] to

of Japanese Unexamined Patent Application Publication (Kokai) No.2008-111103 and Japanese Unexamined Patent Application Publication(Kokai) No. 2009-080474.

The amount of radical generator or photo-acid generator is preferably ina range of 0.1 to 50 parts by mass on the basis of 100 parts by mass ofthe resin.

[Tackifier]

The inventive adhesive composition may contain a tackifier in order tohave tackiness to a living body. Illustrative examples of such atackifier include silicone resin, as well as non-crosslinkable siloxane,non-crosslinkable poly(meth)acrylate, and non-crosslinkable polyether.

[Organic Solvent]

The inventive adhesive composition may contain organic solvent.Illustrative examples of the organic solvent include aromatichydrocarbon solvent such as toluene, xylene, cumene,1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,styrene, α-methylstyrene, butylbenzene, sec-butylbenzene,isobutylbenzene, cymene, diethylbenzene, 2-ethyl-p-xylene,2-propyltoluene, 3-propyltoluene, 4-propyltoluene,1,2,3,5-tetramethyltoluene, 1,2,4,5-tetramethyltoluene,tetrahydronaphthalene, 4-phenyl-1-butene, tert-amylbenzene, amylbenzene,2-tert-butyltoluene, 3-tert-butyltoluene, 4-tert-butyltoluene,5-isopropyl-m-xylene, 3-methylethylbenzene, tert-butyl-3-ethylbenzene,4-tert-butyl-o-xylene, 5-tert-butyl-m-xylene, tert-butyl-p-xylene,1,2-diisopropylbenzene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene,dipropylbenzene, 3,9-dodecadiyne, pentamethylbenzene, hexamethylbenzene,hexylbenzene, and 1,3,5-triethylbenzene; aliphatic hydrocarbon solventsuch as n-heptane, isoheptane, 3-methylhexane, 2,3-dimethylpentane,3-ethylpentane, 1,6-heptadiene, 5-methyl-1-hexyn, norbornane,norbornene, dicyclopentadiene, 1-methyl-1,4-cyclohexadiene, 1-heptyne,2-heptyne, cycloheptane, cycloheptene, 1,3-dimethylcyclopentane,ethylcyclopentane, methylcyclohexane, 1-methyl-1-cyclohexene,3-methyl-1-cyclohexene, methylenecyclohexane, 4-methyl-1-cyclohexene,2-methyl-1-hexene, 2-methyl-2-hexene, 1-heptene, 2-heptene, 3-heptene,n-octane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane,2,5-dimethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane,3-ethyl-2-methylpentane, 3-ethyl-3-methylpentane, 2-methylheptane,3-methylheptane, 4-methylheptane, 2,2,3-trimethylpentane,2,2,4-trimethylpentane, cyclooctane, cyclooctene,1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane,1,4-dimethylcyclohexane, ethylcyclohexane, vinylcyclohexane,isopropylcyclopentane, 2,2-dimethyl-3-hexene, 2,4-dimethyl-1-hexene,2,5-dimethyl-1-hexene, 2,5-dimethyl-2-hexene, 3,3-dimethyl-1-hexene,3,4-dimethyl-1-hexene, 4,4-dimethyl-1-hexene, 2-ethyl-1-hexene,2-methyl-1-heptene, 1-octene, 2-octene, 3-octene, 4-octene,1,7-octadiene, 1-octyne, 2-octyne, 3-octyne, 4-octyne, n-nonane,2,3-dimethylheptane, 2,4-dimethylheptane, 2,5-dimethylheptane,3,3-dimethylheptane, 3,4-dimethylheptane, 3,5-dimethylheptane,4-ethylheptane, 2-methyloctane, 3-methyloctane, 4-methyloctane,2,2,4,4-tetramethylpentane, 2,2,4-trimethylhexane,2,2,5-trimethylhexane, 2,2-dimethyl-3-heptene, 2,3-dimethyl-3-heptene,2,4-dimethyl-1-heptene, 2,6-dimethyl-1-heptene, 2,6-dimethyl-3-heptene,3,5-dimethyl-3-heptene, 2,4,4-trimethyl-1-hexene,3,5,5-trimethyl-1-hexene, 1-ethyl-2-methylcyclohexane,1-ethyl-3-methylcyclohexane, 1-ethyl-4-methylcyclohexane,propylcyclohexane, isopropylcylohexane, 1,1,3-trimethylcyclohexane,1,1,4-trimethylcyclohexane, 1,2,3-trimethylcyclohexane,1,2,4-trimethylcyclohexane, 1,3,5-trimethylcyclohexane,allylcyclohexane, hydrindane, 1,8-nonadiene, 1-nonyne, 2-nonyne,3-nonyne, 4-nonyne, 1-nonene, 2-nonene, 3-nonene, 4-nonene, n-decane,3,3-dimethyloctane, 3,5-dimethyloctane, 4,4-dimethyloctane,3-ethyl-3-methylheptane, 2-methylnonane, 3-methylnonane, 4-methylnonane,tert-butylcyclohexane, butylcyclohexane, isobutylcyclohexane,4-isopropyl-1-methylcyclohexane, pentylcyclopentane,1,1,3,5-tetramethylcyclohexane, cyclododecane, 1-decene, 2-decene,3-decene, 4-decene, 5-decene, 1,9-decadiene, decahydronaphthalene,1-decyne, 2-decyne, 3-decyne, 4-decyne, 5-decyne, 1,5,9-decatriene,2,6-dimethyl-2,4,6-octatriene, limonene, myrcene,1,2,3,4,5-pentamethylcyclopentadiene, α-phellandrene, pinene, terpinene,tetrahydrodicyclopentadiene, 5,6-dihydrodicyclopentadiene,dicyclopentadiene, 1,4-decadiyne, 1,5-decadiyne, 1,9-decadiyne,2,8-decadiyne, 4,6-decadiyne, n-undecane, amylcyclohexane, 1-undecene,1,10-undecadiene, 1-undecyne, 3-undecyne, 5-undecyne,tricyclo[6.2.1.0^(2,7)]undeca-4-ene, n-dodecane, 2-methylundecane,3-methylundecane, 4-methylundecane, 5-methylundecane,2,2,4,6,6-pentamethylheptane, 1,3-dimethyladamantane, 1-ethyladamantane,1,5,9-cyclododecatriene, 1,2,4-trivinylcyclohexane, isoparaffin; ketonesolvent such as cyclohexanone, cyclopentanone, 2-octanone, 2-nonanone,2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone,diisobutyl ketone, methylcyclohexanone, and methyl n-pentyl ketone;alcohol solvent such as 3-methoxybutanol, 3-methyl-3-methoxybutanol,1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ether solvent such aspropylene glycol monomethyl ether, ethylene glycol monomethyl ether,propylene glycol monoethyl ether, ethylene glycol monoethyl ether,propylene glycol dimethyl ether, diethylene glycol dimethyl ether,diisopropyl ether, diisobutyl ether, diisopentyl ether, di-n-pentylether, methyl cylopentyl ether, methyl cyclohexyl ether, di-n-butylether, di-sec-butyl ether, diisopentyl ether, di-sec-pentyl ether,di-tert-amyl ether, di-n-hexyl ether, and anisole; ester solvent such aspropylene glycol monomethyl ether acetate, propylene glycol monoethylether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, propylene glycol mono-tert-butyl ether acetate;lactone solvent such as γ-butyrolactone.

The amount of organic solvent is preferably in a range of 10 to 50,000parts by mass on the basis of 100 parts by mass of the resin.

[Carbon Material]

The inventive adhesive composition can contain a carbon material as anelectric conductivity improver to further enhance the electricconductivity. Illustrative examples of the carbon material includecarbon black and carbon nanotube. The carbon nanotube may be eithersingle layer or multilayer, and the surface may be modified with anorganic group(s). The amount of carbon material is preferably in a rangeof 1 to 50 parts by mass on the basis of 100 parts by mass of the resin.

[Electric Conductivity Improver Other than Carbon Material]

The inventive adhesive composition also can contain an electricconductivity improver other than the carbon material. Illustrativeexamples thereof include particles of resin coated with noble metal suchas gold, silver, and platinum; nanoparticles of gold, silver, andplatinum; as well as particles of metal oxide such as indium-tin oxide(ITO), indium-zinc oxide (IZO), tin oxide, and zinc oxide.

The electric conductivity can also be improved by adding a compound thatcontains a polyether group. The ionic conductivity is improved by ionhopping on the polyether group in which ether groups are repeated. Thepolyether group can be introduced by a method such as addition of apolymer, for example polyethylene glycol, or siloxane having a polyethergroup. These methods are particularly effective in case of siliconetackiness agent (adhesive mass). In case of silicone tackiness agentthat is cured by addition reaction with platinum catalyst, addition ofpolyethylene glycol, the terminal hydroxy groups of which aresubstituted by allyl groups and so on, allows the silicone to integratewith the polyethylene glycol by addition reaction and to decrease theirritativeness to skin. The electric conductivity can also be improvedby adding an ammonium salt that has a polyether chain. Additionally, theelectric conductivity can also be improved by using an acrylic tackinessagent that has a polyether group or an urethane tackiness agent that hasa polyether group on the main chain.

As described above, the inventive adhesive composition can form a livingbody contact layer for a bio-electrode that can efficiently conductelectric signals from skin to a device (i.e., having excellent electricconductivity), is free from the risk of causing allergies even when itis worn on skin for a long time (i.e., having excellentbiocompatibility), is light in weight, can be manufactured at low cost,and does not cause large lowering of the electric conductivity even whenit is wetted with water or dried. The electric conductivity can be moreimproved by adding a carbon material, and a bio-electrode withparticularly high adhesion and high elasticity can be manufactured bycombining resin with tackiness and elasticity. The elasticity andtackiness to skin can be improved by additives, and can be adjusted byadjusting the composition of the resin and the thickness of the livingbody contact layer appropriately.

<Bio-Electrode>

The present invention also provides a bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material; wherein the living body contactlayer is a cured material of the inventive adhesive compositiondescribed above.

Hereinafter, the inventive bio-electrode will be specifically describedby reference to the FIGS., but the present invention is not limitedthereto.

FIG. 1 is a schematic sectional view showing an example of the inventivebio-electrode. The bio-electrode 1 of FIG. 1 has the electro-conductivebase material 2 and the living body contact layer 3 formed on theelectro-conductive base material 2. The living body contact layer 3 is alayer in which the electro-conductive material (salt) 4 and the carbonmaterial 5 are dispersed in the resin 6.

When using the bio-electrode 1 of FIG. 1, electric signals are pickedfrom the living body 7 through the salt 4 and the carbon material 5while bringing the living body contact layer 3 (i.e., the layer in whichthe salt 4 and the carbon material 5 are dispersed in the resin 6) intocontact with the living body 7, and then conducted to a sensor device(not shown) through the electro-conductive base material 2 as shown inFIG. 2. As described above, the inventive bio-electrode can cope withboth electric conductivity and biocompatibility by using the saltdescribed above, can improve the electric conductivity further by addingelectric conductivity improver such as a carbon material in accordancewith needs, and can obtain electric signals from skin stably in highsensitivity because the contact area with skin is kept constant due tothe tackiness thereof.

Hereinafter, each component composing the inventive bio-electrode willbe more specifically described.

[Electro-Conductive Base Material]

The inventive bio-electrode comprises an electro-conductive basematerial. This electro-conductive base material is usually connectedelectrically with a sensor device and so on, and conduct electricalsignals picked from a living body through the living body contact layerto the sensor device and so on.

As the electro-conductive base material, any electro-conductive materialcan be used without being limited to particular ones. However, it ispreferable to comprise one or more species selected from gold, silver,silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron,copper, nickel, stainless, chromium, titanium, and carbon, for example.

The electro-conductive base material may be a hard electro-conductivesubstrate, an electro-conductive film having flexibility, a cloth withthe surface being coated with electro-conductive paste, and a cloth intowhich electro-conductive polymer is kneaded without being limited toparticular substrates. The electro-conductive substrate may be flat,uneven, or mesh-form of woven metal wires, which can be appropriatelyselected in accordance with the use of the bio-electrode.

[Living Body Contact Layer]

The inventive bio-electrode comprises a living body contact layer formedon the electro-conductive base material. This living body contact layer,which is a part to be actually in contact with a living body when usingthe bio-electrode, has electric conductivity and tackiness. The livingbody contact layer is a cured material of the inventive adhesivecomposition described above, that is to say, an adhesive resin layerthat contains the resin and the electro-conductive material (salt)described above, together with additives such as a carbon material inaccordance with needs.

The living body contact layer preferably has adhesion in a range of 0.5N/25 mm or more and 20 N/25 mm or less. The adhesion is commonlymeasured by the method shown in JIS Z 0237, in which a metal substratesuch as a stainless steel (SUS) substrate or a polyethyleneterephthalate (PET) substrate can be used as a base material or,alternatively, human skin can be used for measuring. Human skin haslower surface energy compared to metals and various plastics, whichenergy is as low as that of Teflon (registered trade mark), and is hardto adhere.

The living body contact layer of the bio-electrode preferably has athickness of 1 μm or more and 5 mm or less, more preferably 2 μm or moreand 3 mm or less. A thinner living body contact layer has loweradhesion, but has improved flexibility and lighter weight to improvecompatibility with skin. The thickness of the living body contact layercan be selected based on the balance of adhesion and texture.

The inventive bio-electrode may be provided with a tacky film separatelyon the living body contact layer as previous bio-electrodes (e.g., thebio-electrode described in Japanese Unexamined Patent ApplicationPublication No. 2004-033468) in order to prevent peeling off of thebio-electrode from a living body during the use. When the tacky film isprepared separately, the tacky film may be formed by using a rawmaterial for the tacky film such as an acrylic type, an urethane type,and a silicone type. Particularly, the silicone type is suitable becauseof the high transparency of oxygen, which enables breathing through theskin while pasting the same, the high water repellency, which decreaseslowering of tackiness due to perspiration, and the low stimuli to skin.It is to be noted that the inventive bio-electrode does not necessarilyrequire the tacky film that is prepared separately described above,because peeling off from a living body can be prevented by addingtackifier to the adhesive composition or using a resin having goodtackiness to a living body as described above.

When the inventive bio-electrode is used as a wearable device, thecomponents such as wiring between the bio-electrode and a sensor devicemay be any material without being limited to particular ones. Forexample, it is possible to apply the ones described in JapaneseUnexamined Patent publication (Kokai) No. 2004-033468.

As described above, the inventive bio-electrode can efficiently conductelectric signals from skin to a device (i.e., having excellent electricconductivity), is free from the risk of causing allergies even when itis worn on skin for a long time (i.e., having excellentbiocompatibility), is light in weight, can be manufactured at low cost,and does not cause large lowering of the electric conductivity even whenit is wetted with water or dried, because the living body contact layeris formed from a cured material of the inventive adhesive compositiondescribed above. The electric conductivity can be more improved byadding a carbon material, and a bio-electrode with particularly highadhesion and high elasticity can be manufactured by combining resin withtackiness and elasticity. The elasticity and tackiness to skin can beimproved by additives, and can be adjusted by adjusting the compositionof the resin and the thickness of the living body contact layerappropriately. Accordingly, the inventive bio-electrode described aboveis particularly suitable as a bio-electrode used for a medical wearabledevice.

<Method for Manufacturing Bio-Electrode>

The present invention also provides a method for manufacturing abio-electrode having an electro-conductive base material and a livingbody contact layer formed on the electro-conductive base material,comprising: applying the inventive adhesive composition described aboveonto the electro-conductive base material; and curing the adhesivecomposition; thereby forming the living body contact layer.

The same electro-conductive base material and adhesive composition asdescribed above can be used for the inventive method for manufacturing abio-electrode.

As the method for applying the adhesive composition onto theelectro-conductive base material, any method can be used without beinglimited to particular ones; and dip coating, spray coating, spincoating, roll coating, flow coating, doctor coating, screen printing,flexographic printing, gravure printing, and inkjet printing aresuitable.

The method for curing the resin can be appropriately selected based on akind of resin used for the adhesive composition without being limited toparticular methods. For example, the resin is preferably cured by eitheror both of heat and light. The foregoing adhesive composition can alsobe cured by adding a catalyst to generate acid or base, which causes acrosslinking reaction.

In case of heating, the temperature may be appropriately selected basedon a kind of resin used for the adhesive composition without beinglimited to particular temperature. For example, it is preferable to beabout 50 to 250° C.

When the heating and light irradiation are combined, it is possible toperform the heating and the light irradiation simultaneously, to performthe heating after the light irradiation, or to perform the lightirradiation after the heating. It is also possible to perform air-dryingto evaporate solvent before heating the coating film.

As described above, the inventive method for manufacturing abio-electrode can manufacture the inventive bio-electrode easily and atlow cost, which has excellent electric conductivity and biocompatibilityas well as light weight without causing large lowering of the electricconductivity even when it is wetted with water or dried.

The present invention also provide a salt shown by the following generalformula (2):

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; R⁶ to R¹¹ eachindependently represent a hydrogen atom, a linear, branched, or cyclicalkyl group having 1 to 20 carbon atoms, a linear, branched, or cyclicalkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom; and Y represents a linear or branchedalkylene group having 2 to 16 carbon atoms optionally having one or moregroups selected from an ester group and a thioester group.

Examples of R¹ include the ones illustrated as the foregoing R¹.

Examples of the anion to compose the salt shown by the general formula(2) include the ones illustrated as the fluorosulfonate anion of thesalt shown by the foregoing general formula (1-1) or (1-2) andsatisfying the general formula (2) of the anion. Examples of the cationto compose the salt shown by the general formula (2) include the similarones illustrated as the cation that has two ammonium cation structuresof the salt shown by the foregoing general formula (1-2).

Such a salt, having excellent electric conductivity and extremely lowsolubility in water, is suitable as an electro-conductive material usedfor the inventive adhesive composition, in particular.

EXAMPLES

Hereinafter, the present invention will be specifically described byreference to Examples and Comparative Examples, but the presentinvention is not limited thereto. Incidentally, “Me” represents a methylgroup, and “Vi” represents a vinyl group.

The following are Ammonium salts 1 to 17 and Comparative Ammonium salts1 to 3 each blended to the adhesive composition solution as anelectro-conductive material.

The following are Siloxane Compounds 1 to 3 each blended to the adhesivecomposition solution as silicone resin.

(Siloxane Compound 1)

Siloxane Compound 1 was vinyl group-containing polydimethylsiloxanehaving an alkenyl group-content of 0.007 mol/100 g in which theterminals of molecular chains were blocked with SiMe₂Vi groups, with the30% toluene solution having a viscosity of 27,000 mPa·s.

(Siloxane Compound 2)

Siloxane Compound 2 was a 60% toluene solution of polysiloxane of MQresin composed of an Me₃SiO_(0.5) unit and an SiO₂ unit (Me₃SiO_(0.5)unit/SiO₂ unit=0.8).

(Siloxane Compound 3)

Siloxane Compound 3 was a polydimethylsiloxane-bonded MQ resin obtainedby heating a solution composed of 40 parts by mass of vinylgroup-containing polydimethylsiloxane having an alkenyl group-content of0.007 mol/100 g in which the terminals of molecular chains were blockedwith OH groups, with the 30% toluene solution having a viscosity of42,000 mPa·s; 100 parts by mass of 60% toluene solution of polysiloxaneof MQ resin composed of an Me₃SiO_(0.5) unit and an SiO₂ unit(Me₃SiO_(0.5) unit/SiO₂ unit=0.8); and 26.7 parts by mass of toluenewith refluxing for 4 hours, followed by cooling.

As a silicone resin, KF-353 manufactured by Shin-Etsu Chemical Co., Ltd.was used, which is polyether type silicone oil with the side chain beingmodified with polyether.

The following is Acrylic polymer 1 blended to the adhesive compositionsolution as an acrylic type resin.

(the repeating number in the formula is an average value) Acrylicpolymer 1:

Molecular weight (Mw)=103,000

Dispersity (Mw/Mn)=2.10

The following are Silicone urethane acrylate 1 and 2, Silicone acrylate1 and 2, as well as Silicon methacrylate 1 each blended to the adhesivecomposition solution as a silicone type, an acrylic type, or an urethanetype resin.

(each repeating number in the formulae is an average value).

The following is polyether blended to the adhesive composition solutionas an electric conductivity improver.

The following are materials to be cured by heating for forming anurethane film.

The following are organic solvents each blended to the adhesivecomposition solution.

PGMEA: propylene glycol-1-monomethyl ether-2-acetatePGME: propylene glycol-1-monomethyl ether

The following are a radical generator, and electric conductivityimprovers (carbon black, carbon nanotube, Au-coated particle, Ag-coatedparticle, and ITO particle) blended to the adhesive composition solutionas an additive.

Radical generator: V-601 manufactured by Wako Pure Chemical Industries,Ltd.Carbon black: DENKA BLACK HS-100 manufactured by Denka Co., Ltd.Carbon nanotube: carbon nanotube having a diameter of 0.7 to 1.1 nm anda length of 300 to 2,300 nm manufactured by Sigma-Aldrich Co. LLC.Au-coated particle: Micropearl AU (the diameter of 3 μm) manufactured bySEKISUI CHEMICAL CO. LTD.Ag-coated particle: Ag-coated powder (the diameter of 30 μm)manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.ITO particle: ITO powder (the diameter of 0.03 μm) manufactured byMitsubishi Materials Electronic Chemicals Co., Ltd.

Examples 1 to 21, Comparative Examples 1 to 4

The electro-conductive material (ammonium salt), resin, organic solvent,and additives (a radical generator, electric conductivity improver) wereblended on the basis of the composition described in Table 1 and Table 2to prepare each adhesive composition solution (Adhesive compositionsolutions 1 to 21, Comparative Adhesive composition solutions 1 to 4).

TABLE 1 Electro- Organic Adhesive conductive solvent compositionmaterials Resin (parts by Additives solutions (parts by mass) (parts bymass) mass) (parts by mass) Adhesive composition Ammonium Siloxanecompound 1 (40) toluene (30) Radical generator (4) solution 1 Salt 1(8.5) Siloxane compound 2 (100) Carbon black (10) Adhesive compositionAmmonium Siloxane compound 3 (126) heptane (44) Radical generator (4)solution 2 Salt 2 (10) Carbon black (10) Adhesive composition AmmoniumSiloxane compound 1 (20) toluene (30) Radical generator (4) solution 3Salt 3 (13.5) Siloxane compound 2 (100) PGMEA (14) Carbon black (10)Acrylic polymer 1 (20) Adhesive composition Ammonium Siloxane compound 3(126) toluene (30) Radical generator (4) solution 4 Salt 4 (8.1) PGMEA(14) Carbon black (10) Adhesive composition Ammonium Siloxane compound 3(126) toluene (44) Radical generator (4) solution 5 Salt 5 (9.6) Carbonblack (10) Adhesive composition Ammonium Siloxane compound 3 (100)toluene (30) Radical generator (4) solution 6 Salt 6 (12.3) KF-353 (26)2-heptanone Carbon black (10) (14) Adhesive composition AmmoniumSiloxane compound 3 (126) toluene (30) Radical generator (4) solution 7Salt 7 (7.8) PGME (14) Carbon black (10) Adhesive composition AmmoniumSiloxane compound 3 (126) toluene (44) Radical generator (4) solution 8Salt 8 (8.9) Carbon black (10) Adhesive composition Ammonium Siloxanecompound 3 (126) toluene (44) Radical generator (4) solution 9 Salt 9(10.2) Carbon black (10) Adhesive composition Ammonium Siloxane compound3 (106) toluene (30) Radical generator (4) solution 10 Salt 2 (10)Silicone urethane PGME (14) Carbon nanotube (2) acrylate 1 (20) Adhesivecomposition Ammonium Siloxane compound 3 (106) toluene (30) Radicalgenerator (4) solution 11 Salt 2 (10) Silicone urethane PGME (14)Au-coated particle (20) acrylate 2 (20) Adhesive composition AmmoniumSiloxane compound 3 (106) toluene (30) Radical generator (4) solution 12Salt 2 (10) Silicone acrylate 1 (20) PGME (14) Ag-coated particle (20)Adhesive composition Ammonium Siloxane compound 3 (106) toluene (30)Radical generator (4) solution 13 Salt 2 (10) Silicone acrylate 2 (20)PGME (14) ITO particle (20) Adhesive composition Ammonium Siloxanecompound 3 (116) toluene (30) Radical generator (4) solution 14 Salt 10(15) Silicone methacrylate PGME (14) Carbon black (10) 1 (10) Adhesivecomposition Ammonium Siloxane compound 3 (106) toluene (30) Radicalgenerator (4) solution 15 Salt 11 (15) Silicone urethane PGME (14)Carbon black (10) acrylate 1 (20) Adhesive composition Ammonium Siloxanecompound 3 (106) toluene (30) Radical generator (4) solution 16 Salt 12(15) Silicone urethane PGME (14) Carbon black (10) acrylate 1 (20)

TABLE 2 Electro- Organic Adhesive conductive solvent compositionmaterials Resin (parts by Additives solutions (parts by mass) (parts bymass) mass) (parts by mass) Adhesive composition Ammonium Siloxanecompound 3 (126) toluene (44) Radical generator (4) solution 17 Salt 13(12) Polyether 1 (5) Carbon black (10) Adhesive composition AmmoniumPolyether 2 (53) — Carbon black (10) solution 18 Salt 14 (12)Dimethylsilicone having hydroxypropyl groups at the both terminals 1(10) Isocyanate compound 1 (50) Adhesive composition Ammonium Polyether2 (53) — Carbon black (10) solution 19 Salt 15 (12) Dimethylsiliconehaving hydroxypropyl groups at the both terminals 1 (10) Isocyanatecompound 1 (50) Adhesive composition Ammonium Polyether 2 (53) — Carbonblack (10) solution 20 Salt 16 (12) Dimethylsilicone havinghydroxypropyl groups at the both terminals 1 (10) Isocyanate compound 1(50) Adhesive composition Ammonium Polyether 2 (53) — Carbon black (10)solution 21 Salt 17 (12) Dimethylsilicone having hydroxypropyl groups atthe both terminals 1 (10) Isocyanate compound 1 (50) ComparativeComparative Siloxane compound 3 (126) toluene (44) Radical generator (4)Adhesive composition Ammonium Carbon black (10) solution 1 salt 1 (4.7)Comparative Comparative Siloxane compound 3 (126) toluene (44) Radicalgenerator (4) Adhesive composition Ammonium Carbon black (10) solution 2salt 2 (8.2) Comparative Comparative Siloxane compound 3 (126) toluene(44) Radical generator (4) Adhesive composition Ammonium Carbon black(10) solution 3 salt 3 (8.4) Comparative — Siloxane compound 3 (126)toluene (44) Radical generator (4) Adhesive composition Carbon black(10) solution 4

(Evaluation of Electric Conductivity)

Each adhesive composition solution was applied onto an aluminum diskhaving a diameter of 3 cm and a thickness of 0.2 mm by using anapplicator. This was air dried at room temperature for 6 hours, followedby curing through baking at 100° C. for 30 minutes under a nitrogenatmosphere by using an oven to produce four pieces of bio-electrodes foreach adhesive composition solution. Thus obtained bio-electrode wasprovided with the living body contact layer 3 at one side and providedwith the aluminum disk 8 at the other side as an electro-conductive basematerial as shown in FIGS. 3(a) and (b). Then, the copper wiring 9 waspasted on the surface of the aluminum disk 8 with adhesive tape at theside that had not been coated with the living body contact layer to forma lead-out electrode, which was connected to an impedance measurementapparatus as shown in FIG. 3 (b). Two pieces of the bio-electrodes 1′were pasted on a human arm at a distance of 15 cm from each other suchthat the side of each living body contact layer was in contact with theskin as shown in FIG. 4. The initial impedance was measured whilealtering the frequency by using an AC impedance measurement apparatusSI1260 manufactured by Solartron. Then, the remained two pieces of thebio-electrodes were immersed in pure water for 1 hour, followed bydrying the water, and used for measuring the impedance on skin by thesame method described above. Each impedance at the frequency of 1,000 Hzare shown in Table 3.

(Evaluation of Tackiness: Measurement of Adhesion)

Each adhesive composition solution was applied onto a polyethylenenaphthalate (PEN) substrate having a thickness of 100 μm by using anapplicator. This was air dried at room temperature for 6 hours, followedby curing through baking at 100° C. for 30 minutes under a nitrogenatmosphere by using an oven to produce an adhesive film. From thisadhesive film, a tape with a width of 25 mm was cut out. This waspressed to a stainless (SUS304) board and allowed to stand at roomtemperature for 20 hours. Then, the tape having adhesive mass attachedthereon was pulled away from the stainless board to an angle of 180° ata speed of 300 ram/min by using a tensile tester to measure the force(N/25 mm) for peeling the tape. The results are shown in Table 3.

(Measurement of Thickness of Living Body Contact Layer)

On each bio-electrode produced in the evaluation test of electricconductivity described above, the thickness of the living body contactlayer was measured by using a micrometer. The results are shown in Table3.

TABLE 3 Thickness of Impedance living body Initial after Adhesivecomposition Adhesion contact layer Impedance water immersion solutions(N/25 mm) (μm) (Ω) (Ω) Example 1 Adhesive composition solution 1 3.4 5051.9E⁴ 2.3E⁴ Example 2 Adhesive composition solution 2 3.5 555 1.8E⁴2.1E⁴ Example 3 Adhesive composition solution 3 3.9 518 2.2E⁴ 2.3E⁴Example 4 Adhesive composition solution 4 3.8 470 1.8E⁴ 2.2E⁴ Example 5Adhesive composition solution 5 3.1 490 2.2E⁴ 3.2E⁴ Example 6 Adhesivecomposition solution 6 4.2 460 1.9E⁴ 2.8E⁴ Example 7 Adhesivecomposition solution 7 3.2 520 1.8E⁴ 2.9E⁴ Example 8 Adhesivecomposition solution 8 3.1 430 1.6E⁴ 1.9E⁴ Example 9 Adhesivecomposition solution 9 3.8 520 1.8E⁴ 2.9E⁴ Example 10 Adhesivecomposition solution 10 2.8 450 1.2E⁴ 2.3E⁴ Example 11 Adhesivecomposition solution 11 2.4 550 3.4E⁴ 3.8E⁴ Example 12 Adhesivecomposition solution 12 2.4 540 3.9E⁴ 4.2E⁴ Example 13 Adhesivecomposition solution 13 2.9 550 7.2E⁴ 8.8E⁴ Example 14 Adhesivecomposition solution 14 1.3 553 2.6E³ 2.9E³ Example 15 Adhesivecomposition solution 15 1.2 560 2.8E³ 3.3E³ Example 16 Adhesivecomposition solution 16 1.3 530 2.6E³ 3.0E³ Example 17 Adhesivecomposition solution 17 3.2 510 1.7E⁴ 1.9E⁴ Example 18 Adhesivecomposition solution 18 3.3 530 1.8E⁴ 2.1E⁴ Example 19 Adhesivecomposition solution 19 1.0 570 2.5E³ 3.0E³ Example 20 Adhesivecomposition solution 20 1.2 580 2.7E³ 1.9E³ Example 21 Adhesivecomposition solution 21 1.3 560 2.8E³ 2.3E³ Comparative ComparativeAdhesive composition 2.3 520 2.2E⁴ 5.3E⁵ Example 1 solution 1Comparative Comparative Adhesive composition 2.2 530 3.2E⁴ 7.3E⁵ Example2 solution 2 Comparative Comparative Adhesive composition 2.6 520 5.2E⁴8.3E⁵ Example 3 solution 3 Comparative Comparative Adhesive composition4.5 540 7.9E⁵ 8.9E⁵ Example 4 solution 4

As shown in Table 3, in each of Examples 1 to 21, the living bodycontact layer of which was formed by using the inventive adhesivecomposition containing the salt with particular structure, the initialimpedance was low and did not largely increased by an order of magnitudeafter the bio-electrodes were immersed to water and dried. That is,Examples 1 to 21 each gave a bio-electrode that had high initialelectric conductivity and did not cause large lowering of the electricconductivity even when it is wetted with water or dried. Thesebio-electrodes of Examples 1 to 21 had good adhesion similar to that ofbio-electrode of Comparative Examples 1 to 3, in which previous salt wasblended, were light in weight and excellent in biocompatibility, andcould be manufactured at low cost.

On the other hand, in each Comparative Examples 1 to 3, the living bodycontact layer of which was formed by using an adhesive compositioncontaining previous salt, the initial impedance was low, but largeincrease of the impedance occurred such that the order of magnitude waschanged after water immersion and drying. That is, each of ComparativeExamples 1 to 3 only gave a bio-electrode, the electric conductivity ofwhich was largely decreased when it was wetted by water and dried,although the initial electric conductivity was high.

Comparative Example 4, in which the living body contact layer was formedby using an adhesive composition without containing salt, did not causelarge increase of impedance by an order of magnitude after it wasimmersed to water and dried because it did not contain salt, but theinitial impedance was high. That is, Comparative Example 4 only gave abio-electrode with low initial electric conductivity.

As described above, it was revealed that bio-electrode, with the livingbody contact layer being formed by using the inventive adhesivecomposition, had excellent electric conductivity, biocompatibility, andadhesion properties to an electro-conductive base material; withoutcausing large lowering of electric conductivity even when it was wettedwith water and dried because the electro-conductive material was heldmore securely; is light in weight, and can be manufactured at low cost.

It is to be noted that the present invention is not restricted to theforegoing embodiment. The embodiment is just an exemplification, and anyexamples that have substantially the same feature and demonstrate thesame functions and effects as those in the technical concept describedin claims of the present invention are included in the technical scopeof the present invention.

1. An adhesive composition comprising a resin and an electro-conductivematerial, wherein the electro-conductive material is an ammonium salt offluorosulfonic acid having 5 or more carbon atoms shown by the followinggeneral formula (1),(R¹—X—Z—SO₃ ⁻)_(n)M^(n+)  (1) wherein, R¹ represents a linear, branched,or cyclic monovalent hydrocarbon group having 1 to 40 carbon atoms andoptionally substituted by a heteroatom or optionally interposed by aheteroatom; X represents any of a single bond, an ether group, an estergroup, and an amide group; Z represents a linear or branched alkylenegroup having 2 to 4 carbon atoms, containing 1 to 6 fluorine atoms, andoptionally containing a carbonyl group; M^(n+) represents a cationhaving one or two ammonium cation structures; and “n” is 1 when thenumber of the ammonium cation structure contained in the M^(n+) is one,or is 2 when the number of the ammonium cation structure contained inthe M^(n+) is two.
 2. The adhesive composition according to claim 1,wherein the electro-conductive material is shown by the followinggeneral formula (1-1) or (1-2),

wherein, R¹ and X have the same meanings as defined above; Rf₁ to Rf₄each independently represent an atom or a group selected from a hydrogenatom, a fluorine atom, a methyl group, an ethyl group, and atrifluoromethyl group, with the proviso that one or more of Rf₁ to Rf₄is a fluorine atom or a trifluoromethyl group, and Rf₁ and Rf₂ areoptionally combined with each other to form a carbonyl group; R² to R¹¹each independently represent a hydrogen atom, a linear, branched, orcyclic alkyl group having 1 to 20 carbon atoms, a linear, branched, orcyclic alkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom, and R² and R³ optionally form a ringwith each other together with the nitrogen atom bonded to R² and R³; andY represents a linear or branched alkylene group having 2 to 16 carbonatoms optionally having one or more groups selected from an ester groupand a thioester group.
 3. The adhesive composition according to claim 1,wherein the electro-conductive material has a polymerizable double bondor a hydroxy group in either or both of the anion and the cation.
 4. Theadhesive composition according to claim 2, wherein theelectro-conductive material has a polymerizable double bond or a hydroxygroup in either or both of the anion and the cation.
 5. The adhesivecomposition according to claim 1, wherein the resin is one or moreresins selected from silicone resin, acrylic resin, and urethane resin.6. The adhesive composition according to claim 2, wherein the resin isone or more resins selected from silicone resin, acrylic resin, andurethane resin.
 7. The adhesive composition according to claim 1,further comprising a carbon material.
 8. The adhesive compositionaccording to claim 2, further comprising a carbon material.
 9. Theadhesive composition according to claim 7, wherein the carbon materialis either or both of carbon black and carbon nanotube.
 10. The adhesivecomposition according to claim 8, wherein the carbon material is eitheror both of carbon black and carbon nanotube.
 11. A bio-electrodecomprising an electro-conductive base material and a living body contactlayer formed on the electro-conductive base material; wherein the livingbody contact layer is a cured material of the adhesive compositionaccording to claim
 1. 12. A bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material; wherein the living body contactlayer is a cured material of the adhesive composition according to claim2.
 13. A bio-electrode comprising an electro-conductive base materialand a living body contact layer formed on the electro-conductive basematerial; wherein the living body contact layer is a cured material ofthe adhesive composition according to claim
 3. 14. The bio-electrodeaccording to claim 11, wherein the electro-conductive base materialcomprises one or more species selected from gold, silver, silverchloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper,nickel, stainless, chromium, titanium, and carbon.
 15. A method formanufacturing a bio-electrode having an electro-conductive base materialand a living body contact layer formed on the electro-conductive basematerial, comprising: applying the adhesive composition according toclaim 1 onto the electro-conductive base material; and curing theadhesive composition; thereby forming the living body contact layer. 16.A method for manufacturing a bio-electrode having an electro-conductivebase material and a living body contact layer formed on theelectro-conductive base material, comprising: applying the adhesivecomposition according to claim 2 onto the electro-conductive basematerial; and curing the adhesive composition; thereby forming theliving body contact layer.
 17. A method for manufacturing abio-electrode having an electro-conductive base material and a livingbody contact layer formed on the electro-conductive base material,comprising: applying the adhesive composition according to claim 3 ontothe electro-conductive base material; and curing the adhesivecomposition; thereby forming the living body contact layer.
 18. Themethod for manufacturing a bio-electrode according to claim 15, whereinthe electro-conductive base material comprises one or more speciesselected from gold, silver, silver chloride, platinum, aluminum,magnesium, tin, tungsten, iron, copper, nickel, stainless, chromium,titanium, and carbon.
 19. A salt shown by the following general formula(2):

wherein, R¹ represents a linear, branched, or cyclic monovalenthydrocarbon group having 1 to 40 carbon atoms and optionally substitutedby a heteroatom or optionally interposed by a heteroatom; R⁶ to R¹¹ eachindependently represent a hydrogen atom, a linear, branched, or cyclicalkyl group having 1 to 20 carbon atoms, a linear, branched, or cyclicalkenyl group or alkynyl group having 2 to 10 carbon atoms, or anaromatic group having 4 to 20 carbon atoms, optionally having one ormore species selected from an ether group, a thiol group, an estergroup, a carbonyl group, a hydroxy group, a nitro group, an amino group,a halogen atom, and a sulfur atom; and Y represents a linear or branchedalkylene group having 2 to 16 carbon atoms optionally having one or moregroups selected from an ester group and a thioester group.